It is well known to secure standing seam roof and wall panels, including translucent panels, to purlin or girt substrates using hidden clips and related clip assemblies. Examples of various of these clip assemblies are shown in U.S. Pat. Nos. 4,184,299, 4,193,247, 4,261,998, 4,495,743, 4,543,760, 4,575,983, 5,001,882, 5,181,360, 5,222,341, 5,363,624, 5,606,838 and 6,164,024. As noted in this prior art, a continuing problem has existed concerning the impact of thermal forces (expansion and contraction) on panels supported and joined together by clip assemblies. By way of example, if clip assemblies are too rigid, damage may occur to the panels or clip assemblies during thermal expansion or contraction. In addition, undesirable noises and wear are caused by frictional panel movement resulting from thermal and other forces, i.e. panels rubbing against the clip assembly, against the fasteners that hold the clip assembly, and against the substrates. Thus, there is a need for a clip assembly for a panel system that reduces the potential for undesirable frictional fiorces.